There are numerous applications where bearings that support either a rotating shaft or a translating shaft must be preloaded to minimize movement of the bearing in the supporting bearing race. Where the bearing is subjected to a transverse loading any movement of the bearing will cause excessive vibration of the shaft. In addition to increasing the wear on the shaft any vibration of the bearing will be transmitted to the bearing race and the supporting structure causing rapid damage and premature destruction of the bearing and supporting structure.
One example of an application where preloading of a bearing in a bearing race is required to minimize excessive wear is a linear actuator for helicopter controls. Any movement of the bearing supporting the actuator shaft produces a vibration in the shaft that is transmitted through the bearing to the supporting housing. For proper operation of such actuators it is required to periodically adjust preloading on the bearings to ensure a tight fitting assembly.
Heretofore, the adjustment of a bearing and supporting structure was a time consuming trial and error procedure. One technique found in the prior art utilized apparatus incorporating shims that were assembled into the supporting structure on a trial and error basis until proper preloading of the bearing was accomplished. This was a time consuming operation and in the example of the helicopter application described above meant removal of the helicopter from operation during the servicing procedure. In the application on helicopters where the bearing torque requires periodic adjustment the amount of operating time lost for servicing of a helicopter becomes excessive.
Another presently available method of adjusting preloading on a bearing utilizes a threaded lock nut that applied a force to the bearing race in a direction generally parallel to the longitudinal axis of the bearing. Such apparatus, is difficult to accurately preset and even more difficult to hold in a desired preloaded condition due to the lock nut relieving the adjustment nut preload. Therefore, again there is a trail-and-error situation between the torque nut and the lock nut.